1. Field of the Invention
The present invention generally relates to a hard disk device and, more particularly, to a hard disk device having a hard disk rotating at a high speed, a carriage having a head slider at the tip thereof, and a magnetic circuit causing the carriage to revolve back and forth alternately, in a housing composed of a base and a cover.
Hard disk devices are being made to have higher recording densities. As the recording density becomes higher, track pitch becomes narrower. Accordingly, the tracking of a head slider needs to be controlled with high precision, and non-repeatable runout (NRRO) has to be restricted to a small extent. The non-repeatable runout is an off-track amount of the head slider from a track on a hard disk, which is not synchronous with rotation of a spindle motor. The non-repeatable runout is expressed in xcexcm.
One of the causes that produce the non-repeatable runout is that airflow caused by the hard disk rotating at a high speed contacts and affects the head slider and an arm. Thereupon, in order to restrict the non-repeatable runout to a small extent, the airflow caused by the hard disk rotating at a high speed needs to be made as stable as possible.
Besides, a hard disk device is preferred to be easy to assemble.
2. Description of the Related Art
FIG. 1 is an illustration of a conventional hard disk device 10, with a cover thereof being removed. The hard disk device 10 comprises a hard disk 13 rotating at a high speed in a clockwise direction indicated by an arrow C, a carriage 15 having a head slider 14 at an end thereof, and a magnetic circuit 16 causing the carriage 15 to revolve back and forth alternately, in a housing 12 composed of a base 11 and the cover (not shown in the figure).
Shrouds 20 and 21 are formed unitarily with the base 11, and surround the hard disk 13. These shrouds 20 and 21 are provided so as to stabilize an airflow 25 on the surface of the hard disk 13 which is caused by the hard disk 13 rotating at a high speed; this restricts the non-repeatable runout to a small amount.
The maximum point to which the carriage 15 is revolved counterclockwise is a position at which a part of the carriage 15 at an opposite end to the head slider 14 contacts the shroud 21, as indicated by a dashed chain line in FIG. 1. In this position, the head slider 14 reaches outside the hard disk 13, whereas a part of the carriage 15 overlaps the hard disk 13.
Therefore, in assembling the hard disk device 10, the hard disk 13 and the carriage 15 are first assembled on an assembly apparatus into an assembly combined in a positional relationship indicated by the dashed chain line in FIG. 1. Then, while keeping this positional relationship, the hard disk 13 and the carriage 15 along with the magnetic circuit 16 are carried together to the base 11 so as to be set thereon.
Since the hard disk 13, the carriage 15 and the magnetic circuit 16 are carried together while the positional relationship therebetween being kept, the process of assembling the hard disk device 10 requires a complicated and costly facility, which to that extent raises the manufacturing cost of the hard disk device 10.
It is a general object of the present invention to provide an improved and useful hard disk device in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a hard disk device having a structure which restricts a non-repeatable runout to a small amount, and can enable the step of incorporating a hard disk into a base and the step of incorporating a carriage into the base to be performed separately.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a hard disk device comprising:
a housing having a base;
a hard disk provided in the housing, the hard disk rotating at a high speed in at least one rotational direction;
a carriage provided in the housing, the carriage having a head slider on one end thereof;
a magnetic circuit provided in the housing, the magnetic circuit causing the carriage to revolve back and forth alternately around an axis; and
a shroud member fixed on the base, the shroud member being a separate member from the base.
According to the present invention, the shroud member can be mounted afterward. In other words, the hard disk, the carriage, and the magnetic circuit can be incorporated into the base before the shroud member is mounted on the base. Thereby, the hard disk and the carriage can be incorporated into the base separately and independently, not by being combined and carried together.
Additionally, in the hard disk device according to the present invention, the shroud member may be positioned in a space between the carriage and the magnetic circuit, the space existing at an upstream position from the axis in the rotational direction of the hard disk.
According to the present invention, the shroud member is positioned in the above-mentioned space so as to stabilize an airflow affecting the head slider, restricting a non-repeatable runout to a small extent effectively.
Additionally, in the hard disk device according to the present invention, the magnetic circuit may have a chamfer at a position opposite an outer periphery of the hard disk, the position being located at an upstream position from the axis in the rotational direction of the hard disk;
the shroud member may have a wedge-like portion having a shape corresponding to a wedge-like space formed between the chamfer and the outer periphery; and
the shroud member may be so positioned that the wedge-like portion enters the wedge-like space.
According to the present invention, the wedge-like portion lengthens a surface of the shroud member opposing the outer periphery of the hard disk. Thus, the shroud member effectively restricts a non-repeatable runout to a small extent.
Additionally, in the hard disk device according to the present invention, the shroud member may have a female screw portion at an undersurface thereof so that the shroud member is fixed on the base by a screw passed from an undersurface of the base through the base into the female screw portion.
According to the present invention, the shroud member can be fixed firmly on the base by the screw.
Additionally, in the hard disk device according to the present invention, the shroud member may have a female screw portion and a positioning hole at an undersurface thereof, the female screw portion having an opening at a lower end thereof, so that the shroud member is fixed on the base in a predetermined direction by being conveyed on the base while being supported on a palette at a position in the same direction by having the opening and the positioning hole passed through by projections on the palette, respectively.
According to the present invention, an apparatus incorporating the shroud member from the palette to the base does not need to change the direction of the shroud member. Additionally, the shroud member can be fixed firmly on the base with an excellent precision.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.